For example, a vehicular electronic component employs a connection structure, which includes a press-fit terminal inserted in a through hole, which is formed in a circuit board. In general, such a press-fit terminal has a center portion having an elongated opening. The center portion having the elongated opening has a largest width, which is set to be greater than a diameter of the through hole in which the press-fit terminal is attached. When the press-fit terminal is inserted in and attached to the through hole, both side portions of the press-fit terminal, which are on the outer side of the opening, urges the inner wall of the through hole. Thus, both the side portions apply a required contact force onto the inner wall of the through hole to form electric contacts. For example, Patent Document 1 discloses an art related to a press-fit terminal.
(Patent Document 1)
Publication of Unexamined Japanese Patent Application No. 2000-505590
A press-fit terminal is demanded to function as an electric contact stably. To function as an electric contact stably, a press-fit terminal desirably has a sufficient contact load to the through hole. In addition, in a configuration in which a large strain occurs in a press-fit terminal, the press-fit terminal may cause a crack. Therefore, a press-fit terminal desirably has a configuration to cause a small strain.
To the contrary, in the disclosure of Patent Document 1, the terminal has an opening (hole) in a curved ellipse shape. Therefore, in the configuration of Patent Document 1, the width of the terminal becomes small in a curve portion of an end of the opening. In particular, the width between an inner wall, which defines the opening, and each side portion of the terminal becomes small. In particular, the side of the tip end of the press-fit terminal is in a shape, in which the width decreases toward the tip end, in consideration to facilitate insertion of the terminal into the through hole, and/or the like. In the configuration of Patent Document 1, the opening has straight line portions (inner boundaries), which are in parallel with each other, extending to a position significantly close to a first end, which is in a curved semicircle shape. Therefore, in the configuration of Patent Document 1, the width between the inner wall of the opening and each tip end of the terminal may become small in a wide region close to the first end. Similarly, in the configuration of Patent Document 1, the terminal of the opening has straight line portions (inner boundaries), which are in parallel with each other, extending to a position significantly close to a second end, which is in a curved semicircle shape. Therefore, it is difficult to secure sufficiently the width between the inner wall of the opening and each tip end of the terminal in a wide region close to the second end. The press-fit terminal having such a configuration, in which the width is small around each end of the opening, may cause a large strain around each end of the opening when being inserted into the through hole. Consequently, the press-fit terminal may cause a crack due to concentration of the stress, and-or the like.